How to generate 5 digit random numbers based on the value given in textbox using asp .net c# [on hold]

I need to develop a web application with a textbox and button that will generate 5 digit random numbers based on the value given in textbox.Suppose if i give 7 in text box for the first time and click generate button i need to generate 7 five digit random numbers i.e 10001,20000,25431,98765,45321,54321,76578 like this 7 five digit random numbers and these generated random numbers should be saved in database.Again if i give another number in text box let it be 4 again i need to generate 4 five digit random numbers but this time the random numbers that are generated should not display the already saved random numbers.How can i do this can anyone help me out as i am new to this.